The fish eye can be adjusted to a large degree using their video program. It will not completely eliminate it, but it will reduce it by a substantial degree.

The basic Hero model, which is what I have, does not have external audio inputs, therefore, you must rely on the built in mic, which is mono only. The newer, and more expensive models, record in stereo and with 360 degree audio, which is something I never knew existed.

Additionally, it appears that the Hero8 has a video monitor, which the inexpensive model that I have does not have. There is several lens selections that can also be utilized that would eliminate fish eye while shooting, but then you would not have the ability to see everything that you would with the ultra-wide angle lens.

Take a look at GoPro Hero8